This invention relates generally to spark plug connectors and more specifically to sealed spark plug connectors for connecting ignition cables to spark plug terminals.
A sealed spark plug connector conventionally comprises a terminal that is attached to the end of an ignition cable and surrounded by an elastomeric boot that is attached to the end of the cable above the terminal. The terminal has a resilient receptacle which snaps onto a ball-like spark plug terminal post when the connector is pushed onto the spark plug providing a mechanical and an electrical connection between the two. When connected, the seal engages the spark plug insulator to provide a sealed environment for the electrical connection.
U.S. Pat. No. 2,904,769 granted to Lawrence R. Sampson et al, Sept. 15, 1959 and U.S. Pat. No. 3,359,526 granted to Roel Bakker, Dec. 19, 1967 exemplify these conventional arrangements which have been in use for many years.
A major disadvantage of such arrangements is that the engaged terminals provide the sole mechanical connection between the spark plug connector and the spark plug as well as the electrical connection between the two. Thus these arrangements require a strong mechanical connection and hence a high terminal engagement force requirement. The requirement for a strong mechanical connection also requires a strong crimp connection between the terminal and the ignition cable and a tensionally strong ignition cable because the spark plug connector is often pulled off the spark plug by pulling on the ignition cable.
It is also known to provide a sealed spark plug connector having a receptacle terminal that transfers disengagement forces to a relatively rigid plastic tube forming tube of the sealing arrangement. See U.S. Pat. No. 4,906,202 granted to Kenneth B. Germ Mar. 6, 1990 and assigned to the assignee of this invention. This arrangement alleviates the pull-off problem somewhat. However, the arrangement still has the disadvantage that the terminal connection provides the sole mechanical connection between the spark plug connector and the spark plug.
It is also known from U.S. Pat. No. 2,943,139 granted to Michael Skunda June 28, 1960 and U.S. Pat. No. 3,050,658 granted to Robert Lay et al Aug. 21, 1962 to provide an arrangement wherein the mechanical and electrical connections between the spark plug connector and the spark plug are separated. These arrangements, however, have several disadvantages. The mechanical connections are bulky and not suitable for modern engine designs such as multi-valve engines where the space available for the spark plug and spark plug connector is very limited. Another disadvantage is that the spark plug connectors are difficult to install.